A jet engine or other various types of engines are generally provided with a duct as ancillary equipment for carrying oily gas or exhaust discharged from the engine. The duct provided for this purpose is required to carry the oily gas or exhaust from the engine without leakage to the outside.
The oily gas or exhaust discharged from an engine is generally high in temperature and high in pressure. In particular, along with improvements in engine performance, the oily gas or exhaust ends to become higher in temperature and higher in pressure. For this reason, the duct used for an engine ends up deforming due to the heat by the oily gas or exhaust, the pressure and the load and as a result is usually formed with a moving part so as to keep from this leading to breakage.
As such a duct moving part, a bellows type, piston ring type, tube seal type, etc. may be illustrated. Among these, from the viewpoint of the reduction of weight and cost, a tube seal type including a seal part is suitably used.
In the tube seal type, usually a tube seal and a carbon bushing are combined for use. However, when using a carbon bushing, there is the inconvenience that use at a high temperature, in particular 400° C. or so, is not possible. On the one hand, for a tube seal able to handle a high temperature, for example, the method of coating the seal surface with a nickel-based flame spraying material, cobalt-based flame spraying material, hard chrome plating, etc. have been proposed (for example, see Patent Document 1).
In Patent Document 1, a tube seal given a hard chrome plating at the seal surface is disclosed. However, with the tube seal described in this document, there was the problem that while the durability under a high temperature environment can be improved, the seal characteristics were insufficient.
Further, this inconvenience occurred not only when coating the seal surface by hard chrome plating as described in Patent Document 1, but also when using the above flame spraying material. When using this flame spraying material to coat a seal surface, the flame sprayed coating surface is rough, so it was necessary to polish the seal surface until the necessary surface smoothness. In particular, when using the flame spraying material to coat the seal surface, to secure the seal performance, it was necessary to coat not only the seal surface of the tube seal, but also the seal surface of the opposing side flange. However, when coating the seal surface of a flange, there was the problem that depending on the shape or size of the flange, this polishing ended up becoming difficult.
On the other hand, Patent Document 2 discloses a solid lubrication roller bearing obtained by coating the surface generating the rolling friction or sliding friction with TiN or TiCN to form a hard layer and forming on this hard layer a solid lubrication coating comprised of lead. Further, Patent Document 3 discloses a bearing obtained by providing the surfaces of the bearing bodies moving relative to each other with a reactive coating of metal compound with one or more types of gas by physical vapor deposition and forming a solid lubricant or oil film on the same.
In these Patent Documents 2 and 3, the hard layer (Patent Document 2) or reactive coating of metal compound (Patent Document 3) is formed by ion plating. However, when forming a hard layer or reactive coating of metal compound by ion plating like in these documents, the thickness ends up becoming an extremely thin one of several microns or so. For this reason, when forming parts of the base material with a small thickness such as the seal surface of a seal part by such a hard layer or reactive coating of metal compound, the durability ends up becoming insufficient and as a result application to the seal part becomes impossible.
Patent Document 1: Japanese Patent Publication (A) No. 2003-120327
Patent Document 2: Japanese Utility Model Publication (U) No. 5-67818
Patent Document 3: Japanese Patent Publication (A) No. 62-258224